(CBS/AP) -- A Jacksonville medical examiner on Tuesday testified that George Zimmerman had "insignificant" injuries that didn't appear to result from multiple impacts against concrete.

Zimmerman, the former neighborhood was volunteer who is standing trial in teenager Trayvon Martin's shooting death, has said that Martin repeatedly slammed his head into the sidewalk and that he shot the teen in self-defense. The medical examiner, Valerie Rao, did not conduct the autopsy on Trayvon Martin and was testifying for the prosecution. She is the medical examiner for Duval, Clay and Nassau counties, reports the Orlando Sentinel - not Seminole County, where the case is being tried.

Rao said she believed Zimmerman's injuries resulted from three impacts, one of which could have been against concrete.

"Looking at the concrete area in the reenactment I was given, it's consistent with his head having come into contact with that rough surface," Rao said, taking the stand Tuesday afternoon.

Rao said she was given photographs of Zimmerman's injuries, along with other evidence including Martin's autopsy photographs and Zimmerman's videotaped account of the fatal struggle.

"The individual who examined him and treated Mr. Zimmerman told him sutures were not required," Rao said. "She put a BandAid on each of them, and that was the extent of the treatment."

Reviewing a video of Zimmerman walking from a police car into the police station the night of the altercation, she said Zimmerman "was not incapacitated in any way. He was very alert and walking in pace with the officers."

Answering questions from prosecutors, Rao said she believed the injuries were too minor to be consistent with repeated slamming on a sidewalk.

"If someone's head is repeatedly slammed against against concrete with great force I would expect lacerations, a lot of injuries that would bleed profusely that would necessitate suturing, so I don't see that in this picture," Rao said.

However, responding to questions by defense attorney Mark O'Mara about whether it was possible to medically exclude the possibility of repeated impacts, Rao conceded it was a possibility.

"Is there any medical evidence to exclude the possibility that the skull was hit on the left side four times?" O'Mara said.

"That's not my opinion, but it could be possible," Rao responded.

Rao also testified that the abrasions on Martin's hands were consistent with him striking someone.

Also on Tuesday, the jury heard a redacted version of an interview Zimmerman gave with Fox News television host Sean Hannity last year. In the interview, Zimmerman said he didn't regret getting out of his car or having his gun with him the evening of the altercation. "I feel it was all God's plan," Zimmerman said in the interview.

The jury also heard from Mark Osterman, a man who described Zimmerman as "the best friend I've ever had."

Osterman, who wrote a book entitled, "Defending Our Friend: The Most Hated Man in America," told the court the version of events that he said Zimmerman recounted to him about the fatal struggle.